Model guide · Reviewed
G-SHOCK GM-2100: Size, Battery Life, Water Resistance & Specs
Short answer
The G-SHOCK GM-2100 is the octagonal GA-2100 with a forged stainless steel bezel, weighing 72 g and measuring 11.8 mm thick.
- Thickness
- 11.8 mm
- Weight
- 72 g (2.5 oz)
- Water resistance
- 200 m / 20 bar
- Power
- 3-year battery
The GM-2100 (2021) wraps the CasiOak's resin case in a stainless steel bezel, which adds about 21 g over the GA-2100 and a polished, dressier look. It shares module 5611 and the same three-year SR726W battery with the GA-2100, and it keeps 200 m water resistance. Casio's all-steel version is a different watch, the GM-B2100, which adds Tough Solar and Bluetooth at 165 g.
GM-2100 specifications
Casio's specifications for the stock GM-2100-1A. Custom builds can differ; see the notes below.
| Reference | GM-2100-1A |
|---|---|
| Module | 5611 |
| Display | Analog-digital |
| Shape | Octagonal, stainless steel bezel |
| Case size (L × W × H) | 49.3 × 44.4 × 11.8 mm (1.94 × 1.75 × 0.46 in) |
| Weight | 72 g (2.5 oz) |
| Case | Resin case with stainless steel bezel |
| Band | Resin |
| Band fits wrists | 145–215 mm (5.7–8.5 in) |
| Water resistance | 200 m (660 ft, 20 bar) |
| Power | Battery: SR726W × 2, about 3 years |
| Tough Solar | No |
| Multi-Band 6 (atomic time) | No |
| Bluetooth | No |
| Light | Double LED (dial and LCD) |
| Launched | 2021 |
| Casio U.S. list price | $220 |
Features
- Stainless steel bezel with hairline finish
- World time (31 time zones, 48 cities + UTC)
- 1/100-second stopwatch
- 24-hour countdown timer
- 5 daily alarms
- Mineral glass
What is the G-SHOCK GM-2100?
The G-SHOCK GM-2100 is the octagonal GA-2100 design with a forged stainless steel bezel, launched in 2021. It uses the same module 5611 and analog-digital layout as the GA-2100.
How big and heavy is the GM-2100?
The GM-2100 measures 49.3 × 44.4 × 11.8 mm and weighs 72 g, according to G-Central's specification sheet. The steel bezel makes it about 21 g heavier than the 51 g GA-2100.
Is the GM-2100 full metal?
No, the stock GM-2100 has a stainless steel bezel over a resin case with a resin band. Casio's full-metal octagon is the GM-B2100, which weighs 165 g and adds Tough Solar and Bluetooth.
Is the GM-2100 water resistant?
The stock GM-2100 is rated 200 m (20 bar) water resistant by Casio, and its stainless steel bezel resists corrosion. Custom metal builds can differ, so ask us to confirm a specific piece before swimming.
How long does the GM-2100 battery last?
The GM-2100 runs about 3 years on two SR726W batteries, the same rating as the GA-2100. It is not solar; Casio's GBM-2100 and GM-B2100 are the solar metal versions.
What module does the GM-2100 use?
The GM-2100 uses Casio module 5611, the same module as the GA-2100. One manual therefore covers both watches.
How much does the GM-2100 cost?
Casio's U.S. list price for the GM-2100-1A is $220, as recorded by G-Central. Bezelwright currently lists 8 custom GM-2100 builds from $200.
Is the GM-2100 right for you?
The GM-2100 suits
- People who want the CasiOak shape with real metal on the wrist.
- A dressier daily G-SHOCK that still weighs well under 100 g.
Look elsewhere if
- Anyone who wants the lightest octagon — the GA-2100 is 21 g lighter.
- Buyers expecting a full-metal case and bracelet — that is the GM-B2100 or a custom full-metal build.
Custom GM-2100 builds: what changes
- Our “Custom GM-2100 Full Metal” builds use a metal case and bracelet, so their size and weight differ from the stock GM-2100 listed here.
- Customized case or bracelet components can affect water resistance; contact us to confirm a specific piece before swimming.
Bezelwright is an independent customizer and is not affiliated with Casio. Specs above describe Casio's stock model.
Custom GM-2100 builds (8, from $200)
Shop all GM-2100 builds
GM-2100
GM-2100
GM-2100
GM-2100
GM-2100 · Full Metal
GM-2100 · Full Metal
GM-2100 · Full Metal
GM-2100 · Full Metal
Sources
Figures describe Casio's stock reference model. Independent references are used where Casio's own page could not be read directly, and cross-checked against Casio's published specs.
- Casio (U.S.): GM-2100-1A steel bezel watch (official Casio, accessed October 25, 2026)
- Casio (Canada): GM-2100-1A specifications (battery) (official Casio, accessed October 25, 2026)
- G-Central: G-SHOCK GM-2100 specifications (independent reference, accessed October 25, 2026)
- G-Central: G-SHOCK GM-B2100 (full metal) specifications (independent reference, accessed October 25, 2026)
- Casio G-SHOCK (UK): Are G-SHOCK watches waterproof or water resistant? (official Casio, accessed October 25, 2026)